Structure of interfolding machine

ABSTRACT

An interfolding machine for sheet material for making a stack of interfolded sheets includes at least one web of material to interfold that is cut into sheets of predetermined length and rolls for partially overlapping the sheets in order to form an overlapped portion between two consecutive sheets. Interfolding rolls are also provided, adapted to produce the stack, as well as a conveyor adapted to convey the partially overlapped sheets in a zone set between the roll and the interfolding rolls. Further, the overlapping portion of the sheets is maintained constant through a plurality of belts and guides facing the belts so that between the belts and the respective guides a channel is formed for conveying the partially overlapped sheets.

FIELD OF THE INVENTION

The present invention relates to the production of paper material instacks of interfolded sheets and, in particular Z interfolded sheets.

BACKGROUND OF THE INVENTION

As well known, in paper converting industry a variety of types ofmachines and of processes exists for making paper tissues, paper towelsand the like by producing stacks of interfolded sheets of a certainheight.

They are obtained folding the sheets in an “interfolded” way, namely arefolded into panels by overlapping at the same time a panel of a previoussheet with a panel of a following sheet. In this way, when pulling asheet from the stack, at the moment of the use also a panel of thefollowing sheet is pulled out, with consequent advantages for certaintypes of uses. Among the possible interfolding ways, stacks of Zinterfolded sheets are known.

Machines are known that use one or more webs of paper, coming from oneor more reels, that are cut into sheets and then supplied offset withrespect to one another on folding counter-rotating rollers.

More precisely, the webs are cut into sheets by means of cutting rollersthat interact alternatively, with relative counter-support rollers.

The overlap between two consecutive sheets occurs just after the cuttingstep and a sequence of overlapping and offset sheets come to the foldingrollers from only one direction.

The interfolded stacking step is accomplished with the aid of foldingelements, which in case of rollers with mechanical folding means,consist of mechanical clamps incorporated in the roller.

More precisely, the cut sheets proceed on a first roller that rotates ata first speed. Then, the pass on a second roller, called “overlap”roller, which rotates at a second speed less than the first. This way,owing to this speed difference a sheet travelling upstream is quickerand partially overlaps a sheet travelling downstream, slower, which israised by means of air blows. The overlapping is carried out for about athird of the sheets sheet length, in order to allow the Z interfoldingarrangement, after the passage through the interfolding rollers.

Between the overlapping roller and the interfolding rollers a conveyingsystem is normally provided having opposite belts, adapted to convey thepartially overlapped sheets. The two belts are counter-rotating andtravel at the same speed, keeping the sheets pressed on one another.

The belts are opposite and consist of a plurality of parallel strings,which extend for all the sheet length of the rollers. To avoid that theyloose the desired overlapped condition of a third of their sheet length,the belts must partially to penetrate each other, causing the sheets todeform.

Furthermore, the presence of opposite belts is a structural complicationfor the machine, thus affecting the encumbrance and the costs.

SUMMARY OF THE INVENTION

It is therefore a feature of the present invention to provide aninterfolding machine that produces stacks of Z interfolded sheets, whichallows to overcome the above drawbacks.

This and other objects are accomplished by the structure of interfoldingmachine, according to the present invention, for making a stack ofinterfolded sheets comprising:

at least one web of material to interfold that is cut into sheets ofpredetermined length;

means for partially overlapping the sheets in order to form anoverlapped portion between two consecutive sheets, where the overlappedportion is a predetermined fraction of said sheet length;

interfolding means adapted to make said stack;

conveying means adapted to convey the partially overlapped sheets in aregion set between the means for partially overlapping and theinterfolding means,

means for keeping unchanged the overlapping fraction of the sheets,comprising a plurality of belts and a plurality of fixed guides facingthe belts so that between the belts and the respective guides a channelis formed for conveying the partially overlapped sheets;

and where the belts have a plurality of teeth oriented towards theguides, the teeth being distanced from each other such that least at onetooth coincides with a respective overlapped portion, and pushes theoverlapped portion against a respective guide, so that the conveyingmeans can convey the partially overlapped sheets along the channelpreventing the overlapping fraction of the sheets from changing.

Preferably the conveying means comprises a couple of conveying rollersarranged along the channel, whereby at an overlapping zone in thechannel upstream from the conveying rollers, where the conveying rollerscan only convey the downstream sheet two overlapping sheets, and theoverlapping fraction of the sheets remains unchanged owing to thepressure of the upstream sheet against the downstream sheet and againstthe guides caused by a tooth, so that the upstream sheet is kept pressedagainst the sheet downstream at the overlapping portion, obtaining aconveying contribution.

Advantageously among the guides rotatable support rollers for the sheetsare provided, the rollers having a boundary that protrudes in thechannel and have a peripheral speed equal to the belts.

Preferably the means for overlapping provide an overlapping roller and atransfer roller, the transfer roller rotate at a speed higher than theoverlapping roller in order to deposit on the overlapping roller thesheets overlapped according to the overlapping fraction.

Advantageously the overlapping fraction is ⅓ of the sheet length, sothat a stack of Z interfolded sheets is obtained.

Preferably the overlapping roller provides a plurality of grooveswherein the belts can pass.

Advantageously the belts run parallel to the guides up to a point asclose as possible to the interfolding means, at such point means beingprovided for deviating the belts, whereby the overlapped portions arekept together by the teeth up to such point.

Preferably driving means are provided for the belts so that the beltshave a peripheral speed substantially the same as the overlappingroller.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristic and the advantages of the interfolding machine,according to the invention, will be made clearer with the followingdescription of an exemplary embodiment thereof, exemplifying but notlimitative, with reference to the attached drawings, in which likereference characters designate the same or similar parts, throughout thefigures of which:

FIG. 1 shows a cross sectional diagrammatical view of an interfoldingmachine, according to the invention;

FIG. 2 shows a cross sectional view of the conveying means of thepartially overlapped sheets between a overlapping roller and theinterfolding rollers;

FIG. 3 shows a cross sectional view of the conveying means that issimilar to FIG. 2 but without the presence of the sheets.

DESCRIPTION OF A PREFERRED EXEMPLARY EMBODIMENT

With reference to FIG. 1, an interfolding machine of a sheet materialfor making a stack of interfolded sheets 1 uses at least one web 2 ofmaterial to interfold, for example paper, non woven fabric. The web 2 iscut by a cutting roller 3 into sheets of predetermined length. The cutsheets, all equal to one another, are carried along the machine and areindicated as 4 a, 4 b, 4 c, 4 d, 4 e, 4 f, 4 g, starting from thecutting point under the cutter 3 up to the point where they areinterfolded.

As well known, at first, the cut sheets 4 a, 4 b proceed on a firstroller 5 that rotates at a first speed, then they pass on a secondroller 6, called “overlapping” roller, which rotates at a second speedless than the first. This way, owing to this speed difference a sheet 4c that travels more quickly slides under the sheet downstream 4 dslower, which is raised at its tail by means of an air blows not shown.The overlapping portion, indicated as 7, between the two sheets 4 c and4 d extends for about a third of their sheet length, in order to allow,downstream of it, to be Z-interfolded, by interfolding rollers 8 and 9that are adapted to make a stack 1.

Among the “overlapping” roller 6 and the interfolding rollers 8,9 aconveying system is provided 10, adapted to convey sheets 4 d,4 e,4 f,partially overlapped, in a corresponding conveying portion.

More precisely, the operation of the overlapping system is the following(see FIG. 1). The overlapping roller 6 turns slower than the transferroller. This causes sheet 4 c, which is transferred by the transferroller to the overlapping roller 6 owing to vacuum systems not shown,taking the shape of a wave. The production of the wave is assisted by aspecial small roller 20. Furthermore, the overlapping roller 6 hasspecial concave recesses, not shown in the drawings, for receiving thesheet, which can thus fold partially at the opposite edge. When the tailof the downstream sheet 4 d, which is still attached to the transferroller 5, travels through the passage that exists between overlappingroller 6 and transfer roller 5, the head of the upstream sheet 4 c istransferred by the transfer roller 5 to the overlapping roller 6. Thisis carried out when the overlapping fraction has a predetermined value,i.e. a third of the sheet length.

The problem that solves the present invention is that of keeping theoverlapping portion 7 unchanged when two consecutive sheets leave the“overlapping” roller 6 and are captured by clamps, not shown, of theinterfolding rollers 8 and 9. This position has to be kept by touchingthe least possible the sheets, for not to crease them and pressing themthe least possible, in order not to cause them to loose thepredetermined shape.

This problem is solved by a system for keeping unchanged the overlappingfraction of sheets 4 d,4 e,4 f comprising a plurality of belts 11 and aplurality of fixed guides 12 facing the belts 11. This way, between thebelts 11 and the respective guides 12 a channel 13 is formed throughwhich the sheets can travel freely.

According to the invention, the belts 11 have a plurality of teeth 14oriented towards the guides 12. The teeth 14 are distanced from eachother for the same sheet length, and are phased as the sheets pass suchthat each tooth 14 coincides with a respective overlapped portion 7.

This way, the teeth 14 press the overlapped portion 7 against thecorresponding guides 12, so that sheets 4 d,4 e,4 f that partiallyoverlapped along channel 13 are prevented from changing the overlappedportion.

The conveying system 10 comprises a couple of conveying rollers 15arranged along the channel, such that at first an overlapping zone 7 inthe channel 13, which is located upstream from the conveying rollers 15,the downstream sheet 4 e is pulled by conveying rollers 15, whereas theupstream sheet 4 d is only pushed. This way, the overlapping fraction ofthe sheets 4 d,4 e remains unchanged owing to the pressure of theupstream sheet 4 d against the downstream sheet 4 e and against theguides by a respective tooth 11. In fact, the upstream sheet 4 d is keptpressed against the downstream sheet 4 e at the overlapping portion 7,obtaining, furthermore, a conveying contribution.

The rollers 15 also have function of support for sheets 4 d,4 e,4 f,since have their boundary that protrudes in the channel 13. Furthermore,they have a peripheral speed equal to belts 11.

The belts 11 consist of parallel string belts that follow a loop aboutrollers 16,17 and about “overlapping” roller 6. The belts 11 areprovided for all the sheet length (not shown) of the “overlapping”roller 6, and travel in a respective plurality of grooves 18 made onroller 6 so that the head of the teeth 14 disappears in the grooves 18in order to push on the overlapping portion 7 between the sheets 4 d and4 e as soon as the belts leave the “overlapping” roller 6.

The belts 11 run parallel to the guides up to a point as close aspossible to the interfolding means 8,9. This is possible by arranging aroller 16 at such point as close as possible to the interfolding means8,9, causing the belts 11 to follow an angle as sharp as possible. Thisway, the overlapped portions 7 of the sheets are kept together by theteeth 14 up to this point.

The belts have a peripheral speed substantially the same as theoverlapping roller 6, by driven roller 17.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the invention that others can, by applyingcurrent knowledge, readily modify and/or adapt for various applicationssuch specific embodiments without undue experimentation and withoutdeparting from the generic concept, and, therefore, such adaptations andmodifications should and are intended to be comprehended within themeaning and range of equivalents of the disclosed embodiments. The meansand materials for carrying out various disclosed functions may take avariety of alternative forms without departing from the invention. It isto be understood that the phraseology or terminology employed herein isfor the purpose of description and not of limitation.

1. Interfolding machine of sheet material for making a stack ofinterfolded sheets, comprising: at least one web of material tointerfold that is cut into sheets of predetermined length; means forpartially overlapping said sheets in order to form an overlapped portionbetween two consecutive sheets, where said overlapped portion is apredetermined fraction of said sheet length; means for interfolding thesheets to form the stack; means for conveying the partially overlappedsheets in a zone set between said means for partially overlapping andthe means for interfolding, and means for keeping constant theoverlapped fraction of the sheets between said conveying means and theinterfolding means.
 2. Interfolding machine according to claim 1,wherein the means for keeping constant the overlapped fraction of thesheets comprises a plurality of belts and a plurality of fixed guidesfacing on the belts, such that between the belts and respective guides,a channel is formed, the belts having a plurality of teeth orientedtowards the guides, and wherein the conveying means comprises a pair ofconveying rollers arranged along the channel, whereby at an overlappedportion in the channel, upstream from the conveying rollers, where onlya downstream sheet is pulled by the conveying rollers, and theoverlapped fraction of the sheets remains constant due to the pressureof the upstream sheet against the downstream sheet and against theguides by the teeth, so that the upstream sheet is kept pressed againstthe downstream sheet at an overlapping zone, a conveying contribution isobtained.
 3. Interfolding machine according to claim 2, wherein theconveying rollers have a boundary that protrudes into the channel andhave a peripheral speed equal to the belts.
 4. Interfolding machineaccording to claim 2, wherein the overlapping roller includes aplurality of grooves where the belts are present.
 5. Interfoldingmachine according to claim 2, wherein the belts run parallel to theguides up to a point as close as possible to the interfolding, at saidpoint means being provided for deviating the belts, whereby theoverlapped portions are kept together by the same speed of the teeth upto the point.
 6. Interfolding machine according to claim 2, additionallycomprising means for driving the belts, such that the belts have aperipheral speed substantially the same as the overlapping roller. 7.Interfolding machine according to claim 1, wherein the means foroverlapping comprises an overlapping roller and a transfer roller, thetransfer roller rotating at a speed higher than the overlapping rollerin order to deposit on the overlapping roller the sheets overlappedaccording to the fraction.
 8. Interfolding machine according to claim 7,wherein the fraction is ⅓ of the sheet length, such that a stack isobtained of Z interfolded sheets.